I am trying to get started on observing the Messier catalog but am finding it a bit frustrating. I was trying to get Cluster M5 tonight simply because I was going to tackle some of the brightest first and it was hanging out there in the northern sky (about 3 degrees off N) at about 52 degrees of altitude, where I thought I should be able to see it. Yes I allowed for true north declination in my setup
What's the best approach to zeroing in on these deep objects? I have a 12" Dob with setting circles, leveling base, and alt angle measuring device. Everything was set correctly for M5 but I couldn't find it where my software said it should be. I was using a 25mm Possel EY to start with to get a wide field of view.
your approach was OK, but I would suggest looking for brighter objects to familiarise yourself with how to get the best out of your gear. Objects like Omega Centauri, M7, Eta Carina are all naked eye objects, so you'll be able to spot these quickly and know how close you are with your gear. Even M8 and M6 are naked eye.
I have a couple of questions for you: how are you calculating the azimuth co-ordinate? Are you using an optical finder too? M5 would be visible in a 50mm finder as a small/tiny fuzzy patch.
Another thing that can help is a star chart, be it a paper one or as a smart phone app. These will allow you to star hop to your desired object. If it is on a smart phone, make sure you set it to "night vision" red image or your eyes won't stand a chance to be dark adapted enough to see faint objects.
All the Messiers should be visble in a 12", although a couple (M74 especially) can be tricky. Mone of the northern ones can be hard. In theory M51, for example, should be visible in Vic, but I have yet to nab it here even in the 20". Hopefully being further North you will get a few of those hard to get Messiers!
Alex's suggestion of using brighter objects to check the accuracy of your procedure is a good one.
The important things to think about with manual setting circles on a dob is that the base need to be REALLY level and if using an inclinometer it must be very accurately aligned. A 25mm plossl in your scope wil give (if I remember correctly) about a 0.8deg FOV so if you are 0.5degs awat from your target it will not be visible.
Can I suggest getting a copy of O'Mearas book on the Messiers ( see http://www.bintel.com.au/Accessories...oductview.aspx) It is an excellent intro to these objects and has hints for observing finding all of them.
Hi Glen,
Having setting circles on my 10" DOB, I know how accurate these can be.
But their accuracy depends on several factors.
You already know about levelling the base, and setting it up accurately allowing for magnetic declination.
So that narrows it down. . .
The question was asked what are you using to obtain your target Alt Az co-ords?
As I am sure you know, Alt Az is constantly changing, and is different depending on what your Longitude and Latitude of observing location. So if you are using a computer program (like Stellarium) you need to have it properly set up for your co-rds and observing time.
When I set up, I find and easy object, say Alpha Crux, and fine tune so the setting circle readings exactly match the Program Co-ords for that TIME. Once you do that, you should be happy to find faint fuzzies all night.
I get my co-ordinates from two software packages, the first being SkyX Light on my laptop which came with my Celstron 130 and which I have used for some time and found it to be accurate on both the Dob and the 130. I also have Skeye on my Android tablet which gave the same information.
As to the finder I have the standard GSO 50x8 right angle finder that ships with the 12" dob. It has worked fine on nearer object.
I should also mention that prior to trying to find M5 I was viewing Saturn last night and my setup was spot on for that near object, which of course was very bright and high in the NE at that time.
I will take your advice and start by going for the brightest possible Ms and verify my approach that way.
I think last night was also compromised by a couple of weather related factors, the first being some high cirrus bands that were in the area around sunset, and the heavy condensation that I had to deal with here on Lake Macquarie, that cut my session time down. The dob has a mirror fan but I haven't done the mod (yet) to isolate it to allow it to run while viewing (without induced image vibration).
There's a few things that will help out when looking for deep sky objects if you are relatively new to astro.
* Most deep sky objects (DSOs) are faint. For this reason we need to give our eyes a couple of minutes to dark adapt, and to keep ambient light to as low as possible. This means that the porch light needs to be off!
* If you need a light, use a torch that's red in colour. Red causes the least amount of disruption to our dark adapted eyes. "Redifying" a torch is easy to do: wrap three or four layers of red cellophane over your torch will do the job. It will also tone down the brightness.
* An optical finder will show a huge number of DSO's. From a dark site, using a 30mm finder, I've been able to spot the galaxies M104, Centaurus A and M83. From my home in Sydney I've seen these three in a 50mm finder (up until 18months ago - light pollution has killed that off), and from a dark site, even Port Macquarie, you should have no trouble. They will be faint though.
* Learn the skill of averted vision. Our human eyes are such that our central focus isn't too crash hot when it comes to low light levels. You'll find that you'll actually see a whole lot more if you look just to one side of the object in question - this area immediately surrounding our central focus is more light sensitive, and still has enough definition in it to make out detail. Our far peripheral vision can make out faint light, but the detail isn't anywhere as good.
* MOVEMENT is your best friend! I'll explain it this way: ever notice that when you walk into a butcher the smell of the meat is quite strong, but after a few moments you don't notice the smell anymore? This is because the smell receptors in our noses have become exhausted through saturation. Our eyes are the same. They are made to pick up the smallest changes in light. You'll notice this when you are looking into the eyepiece, swinging the scope around trying to spot a faint object, and in one instance "flash"!, you saw something and then it's gone! You didn't see things. Your eyes picked up the tiny change in light as the object whizzed through the field of view. You no longer see it as you are trying to use your central focus, which as I mentioned, really won't show up such a small change in light anywhere as well as your averted vision will. So when you go back to look for that thing that you "thought" you saw, DON'T look for it directly, but use averted vision.
This same movement in the eyepiece will also restimulate your eyes if you've been looking at the same thing for some time. Your eyes will become quickly saturated with the low light situation you are looking at, so a little tap on the scope will introduce a little vibration and shake up the image in the EP, and PRESTO! you can see really faint details again!!!
* Take your time. The problem about visual astronomy is that we need to make use of our sight's weakest point - low level illumination. Seeing in low levels of light takes a little time and practice.
Here's an exercise for you, and anyone also new to astro. As long as the scope you are using is 70mm or larger, this exercise is a goer:
Chase down the giant globular cluster Omega Centauri. A first glance it will appear as a big fuzzy round blob. Park your vision just to one edge and hold it steady at the one spot and count to five. As if by magic, a mass of millions of tiny pin points of light will appear all at once! In the excitement you will shift your eyes, and they will all disappear! This is another little trick, where we are allowing our eyes to build up the saturation of faint light so that we can actually see an amazing amount of detail. Have a go. This is how I approach my observation of all globular clusters, large or small, and it still gives me a thrill this exercise after more than 30 years of looking in to eyepieces,
If you'd like to read up on other tips and techniques for improving your observing skills, have a look at this sticky in the Observational and Visual Astronomy forum:
I did that the other week when we had clear skies in se qld ... your tip with Omega Centauri. at the time I just thought me eyes were fooling me but reading your post Alexander I realised I saw what I saw. thanks, I should have clear skies again soon to retry.
like you said, they just pop into thousands of stars and then if ya move your eye to focus, it becomes mush again. I still remember that even after a few too many long necks lol
I'm sure after I saw that I tried hunting Centaurus A ... but with no luck (I'm using a 114/900 reflector) ... I did see something faint ... but I'm sure I was looking for it instead of my eyes finding it with averted vision, which feels kinda funny. would the same 5 second technique work for those kind of objects? sorry I didn't mean to hiijack the thread. I should just save up and buy a dob and explore
Glen's original post I think relates to both the workings of his scope and the observing of objects, so I don't think your question is misplaced here at all.
Galaxies are tricky things to pin. What they ALL require is at least a relatively dark sky to at least catch a glimpse of.
In my last post I mentioned having seen Centaurus A in a 30mm & 50mm finder. A 114 scope is certainly capable to doing so too. What you need to do (I'm assuming you're observing from at least a moderately light polluted sky or better conditions - centre of Gold Coast ain't much good) is use your lowest power/magnification. Cent. A lies nearly due north of Omega Centauri, just a tiny bit east too, not quite the same span as the north-south axis length of the Southern Cross. It can be a right royal miserable task to find sometimes too, . Take your time. If you are getting frustrated, move away from the scope, take a deep breath and try again. You will ping it. Once you've nabbed it, try changing the EPs on it. Increasing the magnification also increases contrast which can help with pulling out detail in galaxies.
The "5 second pause" can work on galaxies, but they are soft extended objects that don't reveal their individual stars. The 5 second pause works on GCs, and concentrated OCs, as it helps the light of the faint stars accumulate on our eyes a little, and then BLING! they appear.
Galaxies are like nebulae. Their detail is extended, and the best way to observe detail in them is by taking time. They both benefit from an occasional tap to the scope to introduce a little vibration or nudge.
Centaurus A in your scope will show that its "meat patty" is wedge shaped. If your vision is upto the task, it might even show a faint filament of light in the wedge that follows the shape of the wedge too.
Why it shows up easier in a finder than a big scope is an interesting thing. We all say "aperture is king", but the 'king' takes many guises. A big scope collects a lot of light, including a lot of the background sky glow. It also spreads out the light a lot more with its intrinsic increase in magnification. A finder (and binos for that matter) doesn't collect as much background light, and with its small amount of magnification, the light of an extended object like a galaxy or nebula, is much more concentrated in a tiny spot, so it can be much easier to see!
This is one reason why I always pack my binos with my scope when going bush. The scope goes right in on detail. The binos give me the BIG picture that a scope just can't. I've included a couple of my sketches to show what I mean. Both are of the same field around M8 and M20. The first is with an 8" scope at 27X showing approximately a 2.25 true field of view (sketch done from my home in Sydney). The second was done using my 11X70 binos from a dark site, appox. 4.5deg true field of view. The first shows detail in the nebulae, and fainter individual stars, but the second shows a much more extensive glow of the nebulae, and a more mottled structure of the background Milky Way, including a dark nebula that would lie outside of the field of view in the scope.
In the end it comes down to using ALL your scope's capabilities, including exploiting the finder, and taking time. This is all low light level stuff.
I'm in relatively decent dark skies, meaning I can go out in the back yard and and see Omega Centauri within about 30 seconds of looking for it naked eye. The Milky Way is well milky... I'm on a hill with only houses either side which sit below my field of view and theres bush behind the back fence.
Agreed the easterly veiw is a bit washed out but I hardly look that way. I've tried locating Cen A by how you said, using a 40mm ep, I kinda used telrad circles in an app and calculating my eye piece tfov to roughly move from Omega Centauri upwards approximately 1.5 ep lengths and hunting around there for Cen A.
When the weather clears up I shall have another go using your techniques you have recommended. I have 12x50 binos that I use a lot when I think I won't have the time to play with the scope, but I mainly just look around without trying to nail anything, and I havnt tried for a galaxy with them, just clusters and nebs.
I will compare your M8/M20 sketches as that's now coming up over the house at a reasonable time (midnightish) ... I havnt had the chance to view that area this year as yet. But I love all the clusters and nebs around there, so much to see, so little time.
Thanks again Mental!
matt
Last edited by noeyedeer; 14-06-2013 at 01:04 AM.
Reason: actually look at the binos and they are 12x50
Well thanks to Mental, Alan, Malcolm, and all the others I have made some real progress on the DSOs, particularly last night.
I managed to view four of the Messier Objects: M4 Globular cluster near Antares, M10 Globular cluster, M6 the Butterfly open cluster, and M7 Ptolemy's open cluster.
On advice I picked up a GSO 30mm Superview 2" eyepiece and this really helped heaps to initially find the objects. My patience in scope alignment, actually setting it up before sunset, and using my laser line designator and Silva compass to align the scope setting circle to north with allowance for proper declination for my location, all ensured the Azi co-ordinates were spot on and the object was right there in my eyepiece with no searching or star hopping required (well the wide FOV helped).
PS I also made up a DIY 450mm long dew shield which worked well to keep the secondary clear for the whole session. And I have a copy of O'Mearas book on the Messiers on the way.
Well done Glen! You are well on your way with the Messiers.
This is the time of year to be getting them with all the galaxies in Virgo, Coma and Leo early and the globs and nebs around Scorpio and Sagittarius all easily seen.
Have a crack at M104 (Sombrero Galaxy) before it gets too low!
. Take your time. If you are getting frustrated, move away from the scope, take a deep breath and try again. You will ping it. Once you've nabbed it, try changing the EPs on it. Increasing the magnification also increases contrast which can help with pulling out detail in galaxies.
